Anti-back-siphoning water supply valve and mixer

ABSTRACT

A low cost portable mixer-dispenser device connectable to a garden hose and supplied with potable water from a municipal water dispensing system in which a non-contamination safety back flow check valve located at the inlet of a water chamber along with a vent valve therebeyond coacts therewith to vent the chamber to atmosphere at a point upstream of a solution mixing chamber. A manual dispensing valve is located at the outlet of the water chamber and the closure and venting of the water chamber occurs when the pressure on the municipal water supply drops to a predetermined low gauge pressure below which maximum degradation of the dilution ratio of the solution is not tolerable for an aspirating jet pump that is located between the manual valve and a dispensing nozzle, thereby serving a dual function of protecting the supply system against contamination and preventing operation if water pressure becomes inadequate to maintain in a proper mixture ratio.

United States Patent 91 [111 3,863,665

Hechler, IV. Feb. 4, 1975 ANTI-BACK-SIPHONING WATER SUPPLY VALVE AND MIXER [57] ABSTRACT [7 Inventor? Valentine Hechlel; 26 Meadow A low cost portable mixer-dispenser device connect- VIEW Northfleld, Ill. 60093 able to a garden hose and supplied with potable water [22] Filed: Man 21, 1974 from a municipal water dispensing system in which a non-contamination safety back flow check valve lo- [21] Appl. No.: 453,290 cated at the inlet of a water chamber along with a vent Related Application Data valve therebeyond coacts therewith to vent the chamber to atmosphere at a point upstream of a solution [62] Division of 333309 1973 mixing chamber. A manual dispensing valve is located abandoned at the outlet of the water chamber and the closure and 52 U.S. Cl. 137 21s vemmg the i l Chamber curs when kg Int Cl 6k 45/00 F04f 7/02 Gosd 1/1/02 sure on the mumcipal water supply drops to a prede- [58] Fie'ld 'f' 137/217 5 239/310 termined low gauge pressure below which maximum 239/318 414 degradation of the dilution ratio of the solution is not tolerable for an aspirating jet pump that is located between the manual valve and a dispensing nozzle, [56] References cued thereby serving a dual function of protecting the sup- UNITED STATES PATENTS ply system against contamination and preventing oper- 3,498,3l0 3/1970 l-lechler 137/218 X ation if water pressure becomes inadequate to maintain in a proper mixture ratio. Primary Examiner-Henry T. Klinksiek Attorney, Agent, or Firm-Harbaugh and Thomas 18 8 Drawmg F'gures PATENTED FEB 41975,

SHEET 1 BF '2 ANTl-BACK-SIPHONING WATER SUPPLY VALVE AND MIXER This is a division, of Application Ser. No. 333,309 filed Feb. 16, 1973, now abandoned.

BACKGROUND OF THE INVENTION In increasing numbers of states, anti-back siphoning devices must be installed at a valve outlet of a potable water distribution system if the valve outlet level from which the water will flow is not above a potential flood level. This requirement in the codes of a few states generally operates to protect the rest of the states on nationally merchandised products. Where valves are used in such devices the performance test generally employed for acceptable protection involves placing a .050" wire in all check valves which are in the path of reverse flow, if there is no adequate vacuum breaker per se, in the pure water line leading from the valve outlet. Most valve devices fail and very few, if any, have passed this test.

Although fertilizers and pest control chemicals can be sprayed into open air without a vacumm breaker but with only a constantly open minimum air gap siphon sprayer at the outlet end of a hose, the handling of the chemical supply along with the nozzle is a deterrent and critical proportioning deficiencies and irregularities are involved.

Vacuum breakers, required in an endeavor to prevent back-flow contamination of a municipal potable water system one sometimes used with dilution mixingdispensing devices located at the end of a garden hose that utilize both the water and its pressure to mix and dispense fertilizer or pest control solutions. As the designation vacuum implies, however, a back flow stops flow and vents to atmosphere when the municipal water supply drops to zero pounds gauge pressure. Contaminating flow back into the municipal supply line may or may not occur.

On the other hand, vacuum breakers are generally located upstream well ahead of flow control valves so that theoretically there can be no back-flow of solution into the municipal supply. However, some mixtures may have already moved back past the check valve before a vacuum gauge pressure occurs or the vacuum breaker operates. Other vacuum breakers are made of an elastomer that can deteriorate and permit dangerous leakage even with the potable water open to atmosphere.

SUMMARY OF PRESENT INVENTION A safety back flow cut-off valve, preferably a slide valve, is located where the potable water enters a potable water chamber whose supply outlet to the mixing chamber is controlled preferably by a two-stage manually opened and closed valve. A vent valve between the two valves opens the chamber to atmosphere to drop the chamber pressure to atmospheric pressure when opened. The cut-off valve is urged to its closed position by a spring exerting an effort in the range of 3 to 10 pounds and the venting valve is coupled therewith'to open immediately following initial closure of the cutoff valve.

With this arrangement a unitized gun type device can be provided to mix and dispense a mixture which includes a safety back flow check valve, a flow control valve, mixing chamber and dispensing nozzle. The gun is connected to the outlet of a potable water supply hose and a predetermined'ratio solution is produced and dispensed under a minimum loss of water supply pressure yet, as a matter of safety, the flow of water and venting of the potable water chamber to atmosphere can sequentially be made when the water gauge pressure drops too low to provide a dilution ratio. This is accomplished regardless of whether or not the pressure may drop further to a point where back-siphoning might otherwise occur. A further safeguard is present wherein the volume of water under pressure in the supply hose continues a positive flow of a hydraulically solid supply to provide a time interval within which the safety components can be activated to avoid danger be fore it occurs. For instance a 150 foot garden hose subjected to 70 p.s.i.g. stores approximately one half gallon of water to provide an operational time lapse for valve actuation before a flow back potential is reached.

The gun serves as a carrying member and a nozzledirecting handle with a concentrate bottle flexibly hung thereto without burdening the movement of the handle for spray purposes other than to support the dead weight of the bottle. This support is a close distance of a few inches so that the gun never gets below the bottle contents when set down. Further, the lift height of the concentrate is negligible and insignificant within ounces for the concentrate because it is aspirated only a short height directly to the jet pump concentrate inlet.

The jet pump preferably is a two-stage jet pump in which converging walls leading to a jet nozzle converts pressure on the water to jet flow energy and the jet is directed into a mixing chamber having a larger flow area than the nozzle where water molecules transfer energy to and entrain molecules of the solution in relation to the differential in sizes to provide a predetermined proportioning ratio and then passing the mixture through expanding walls to convert the energy back to pressure for dispensing through a dispensing nozzle having a flow area substantially less than the water flow area ahead of the jet pump where the water is above a predetermined low pressure.

With great efficiency a substantially constant dilution ratio can be provided with jet pumps in tandem as where the first stage ratio is l to 5 and the output of this is supplied to the second stage at a ratio of l to 5 to provide a l 25 dispensing solution. This ratio can be maintained rather accurately over the expected range of municipal water pressures, particularly with the supply solution close to the level of the gun.

Moreover, with a ball check in the diverging walls of the first stage to protect against any drain of diluted flow back to the concentrate supply and to maintain priming, any back-flow tendency that may be residual in the compartment will be negligible for the mixture remaining in the compartment because below a certain working water supply pressure the aspirating effect will decline to a negligible gauge pressure well before the water supply pressure drops to zero gauge. Then with the first stage mixing chamber closed any back flow at atmospheric pressure through the first stage before zero gauge is prevented. Accordingly, for plural advantages, the safety factor can be related to a critical low water pressure. The safety cut-off for everything can be resolved at the lowest pressure flow for acceptable proportioning of the jet pump mixer. Thereby any potable water pressure below a desired mixing efficiency will not be permitted to continue to flow. This is accomplished by a positive closure of the inlet valve. With this shut-off action of the inlet valve the water chamber is vented to atmosphere while there is still inlet pressure in the potable water supply hose that would prevent back flow into the hose at atmospheric pressure even if there is possible leakage at the closed inlet valve, and back flow of diluted solution in the concentrate supply will be inhibited.

IN THE DRAWINGS:

FIG. 1 is a perspective view of the device embodying the invention as manipulated in use and operation;

FIG. 2 is a longitudinal section through the gunhandle portion of equipment shown in FIG. 1;

FIG. 3 is an enlargement of the valve portion of the sectional view of FIG. 2 with the valves disposed in full liquid flow positions;

FIG. 4 is a view similar to FIG. 3 in which the valves are in full no-flow positions;

FIG. 5 is a view similar to FIGS. 3 and 4 in which the valves are at an intermediate stage of operation;

FIG. 6 is a section taken on lines 66 in FIG. 2;

FIG. 7 is a section taken on line 7-7 in FIG. 2; and

FIG. 8 is a view similar to FIG. 3 showing a simplified modification of the dual flow and the dual action vent valves.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to FIG. 1 in further detail, a unitary housing 10 molded of a plastic is shown having an elongated compartment 11 therethrough with its inlet end 12 comprising a coarsely threaded three-fourths inch opening 14 receiving the outlet fitting 16 of a garden hose I7 whose end 18 seals against a washer 20 having the marginal edge 19 of a screen member 21 embedded therein supported by a flanged insert 22, engaging a housing shoulder 24. The outlet end 26 of the housing is externally threaded with an unconventional thread 28 which prevents standard water garden connections used with gardening equipment being reversely or improperly made. Only an intended outlet fitting such as a spray nozzle 30 can be attached that is open continuously for discharge to atmosphere as at 3].

Spaced from its inlet end 12 the compartment 11 is internally provided with an axial circular flange 32 (FIG. 3) extending towards the inlet 14 and concentric with and radially spaced from the interior wall 33 of the housing to define a ring valve port 34 terminating in radial apertures 35 open to atmosphere.

The flanged insert 22 internally defines a cylindrical port 36 of an inlet slide valve 37 construction having a spider 38 at its inlet supporting a valve guide 40 having a head 42 thereon supporting an almost fully compressed long compression spring 44 at one of its ends whereby its effort at the other end varies very little with its working movement. A U-shaped V-ring valve 46 is reciprocably mounted on the guide 40 with the inner wall 48 thereof sliding in sealed relation on the guide 40 while the outer wall 49 slidably engages the cylindrical wall of the port 36.

A semiconical cup-shaped valve member 52 having flow openings 54 in its walls 56 has its base 58 reciprocably mounted also on the guide 40 where, on its outer side, it supports the edges of the seal 46 with its bottom directed towards the inlet 14 while on its inner side it engages the other end of the compression spring 44 for it to urge the closure of the inlet valve 46. The rim 47 of the valve member 52 is continuous and circular to receive in adhered relation an elastomer V-ring 60 thereon internally of its bight in a position so that the spread walls 61 thereof slidably engage as a valve member 63 the walls 33 and 62 of the ring valve port 34.

As shown in the sequence steps of FIGS. 3-5, the wall 56 serves to direct substantial flow of water from the inlet port 36 against the valve member 63 and its length is such that when the inlet valve 46 is closed, resting against the spider 38, the vent valve member 63 is fully open; and when the vent valve member 63 is fully closed as when engaging the wall 62 beyond the vent openings 35, the inlet valve 46 is wide open. The spacing of the entrance edges of the inlet and vent ports in relation to the length of the wall 56 is such that the inlet valve 46 begins to seal the inlet port 36 before the vent valve 63 begins to open so that in their concerted coacting movement preferably momentarily both valves are closed at the same time during their transition.

It is preferred also that the inlet and vent ports 36 and 34 substantially have the same flow area and the spring 44 exerts a valve closing effect from 3 to 5 pounds, but. if there is a substantial differential it would be with the vent area being the larger for stable conditions. Thereby, with the inlet valve 46 closed and atmospheric pressure present in the compartment II the inlet valve will not open until the inlet pressure opens the inlet valve 46 and in doing so initiates closure of the vent valve 63. Thereafter, with no outlet from the compartment open to atmosphere, the pressure upon the vent valve 63 will drive it to its fully closed position and will thereby overcome any tendency of the inlet valve to be drawn back against a full opening by virtue of the reduced pressure of the high rate of flow passing between the valve and the seat. The spring then supplies the means for urging the inlet valve to close when pressure in the compartment drops below a predetermined pressure. Until then the vent valve holds the inlet valve fully open for full flow operation. In fact, given substantially equal pressures on opposite sides of the inlet valve, the inlet valve 46 is held open by the pressure differential across the vent valve 63. Then as water inlet pressure happens to decrease to a predetermined gauge pressure the opening of the vent valve and closure of the inlet valve can be accomplished by the spring 44.

The vent valve 63 thereby serves as a safety pressure relief to atmosphere when the compartment pressure drops enough for the spring 44 to initiate closure of the inlet valve 46 and therewith initiate the opening of the vent valve 63 while gauge pressure still exists in the inlet compartment. Atmospheric pressure is then sure to take over and prevail in the compartment I1 while some gauge pressure still exists at the inlet valve and the inlet valve 46 is further closed to the extent urged by the spring against the decreasing inlet pressure.

As the input pressure varies, so long as the force developed by pressure against the vent valve exceeds that of the spring force, the inlet valve will remain fully open.

As the pressure diminishes to a point less than the force exerted by the spring, the spring 44 sequentially closes the inlet valve and opens the vent valve. This closing pressure can be predetermined and is at a positive gauge pressure and preferably above that which would be reached at or shortly before the municipal water pressure and flow drops to a point that is inadequate to provide acceptable aspiration of the concentrate and proper proportioning of the mixture of liquids in the mixing chamber as herein described.

Manual control of the flow of water through the compartment is provided by a dual valve arrangement having a low opening effort followed by equalization and a final low effort full opening. Thus, a partial flow, full flow or no-flow operation well within the thumb strength of a housewife is provided to assure adequate working action of a pump jet syphoning device that provides a desired amount of different solutions of proper proportions for various tasks including cleaning detergents.

For this purpose the inside wall of the cylindrical flanged member 32 internally provides a larger cylindrical port 70 (FIGS. 4-6) which receives a radially vaned guide 72 carrying a flanged valve sleeve member 74 supporting a V-ring valve seal member 76 thereon with the edges of the sides 78 of the seal resting against the radial flange 80, to close it as guided by the vanes 72.

The inside face 82 of the wall 84 of the flanged member 32 also provides a cylindrical port 86 with which a smaller area valve 88 cooperates sequentially with the larger area valve member 76. The smaller valve member 88 is preferable an integral part of a single molding which includes the radial guide vanes 72 reduced in their radial dimension at 90 to radially and axially support the sleeve member 74 loosely with a lost motion relationship on the integral stem 92 which in turn terminates forwardly in the smaller valve head 88 having a circumferential groove around it also receiving a V- ring or an O-ring valve seal 94. An O-ring may provide some frictional effect to assist in closing the large valve. The inner end 96 of the stem 92 reciprocably. extends in an axial direction through an'opening 97 (FIG. 1) in a cross wall portion 98 of the housing having a molded cup shape 100 carrying a V-ring 102 seal therein which seals the stem as exposed to atmosphere at its inner end in a recess 110.

In the assembly of the two valves 74 and 88, the stem 96 has the V-ring 102 slipped thereon with the sides of the V-ring disposed towards the valve head 88 and the flanged member 74 in place against the ends 90 of the vanes 72. Thereupon the seal ring 94 is installed and the assembly slipped into its working position as shown in FIG. 3 and then pushed home to the position shown in FIG. 4 with the vanes 72 seating the seal 102.

In operation, the dual valve manually opens sequentially. The stem 96 is moved towards the inlet 14 to open the small valve 88 against water pressure in the compartment 11, only nominal effort being required due to the smallness of the valve area exposed to the pressure. Upon its opening and water flow the pressures are essentially equalized on both sides of the larger valve 76 whereupon it can be easily moved manually to its wide open position by continued movement of the valve stem. Thereafter the valves can be held open manually with little sustained effort and when released the pressure upon the stem 92 at the seal 102, even at low pressures is enough to urge closure of the valves when manually released.

Referring to FIG. 8 a modification is shown in which a feel" of opening the larger valve 74 is assured by eliminating the valve guide 40 and spacer 43 ofFlG. 4 and extending the spring 44. The extended spring 44A is much longer and is of such initial length thatits 6 change of effort in its working length is greatly minimized to provide an action equivalent to that performed by the spring 44 in FIG. 4 when both valves 44 and 76 are wide open. j

The small valve 88 is integrally formed with an elongated guide rod which also serves as a push rod 92A which is slidably supported at its opposite ends. The inlet end is slidable in a spider 38A and its other end is slidably supported on the housing for manual actuation as later described. The cup member 52A is slidably mounted upon the rod 92A at its inlet end with the V- ring seal 46 carried on the end wall 58 thereof.

The wall 56A of the cup member 52A is longitudinally slotted and elements thereby formed adjacent eachslit 50 are alternately offset radially inwardly and outwardly to provide radially spaced longitudinal guides 53 and 55. Otherwise, the cup 52A if molded can be molded to the shape shown. The guides 55 slidably engage the inner wall 33 of the housing 10 in guided relation while the inner guides 53 guidethe flange member 74A modified to carry a cylindrical flange 57 to be slidably guided by the inner guides 53 in its excursion. The guides 53 also prevent the spring 44A from buckling. The spaces 64 made at the slits 50 by the radially spaced guides provide full flow openings 54. The spider in this instance slidably supports the push rod 92A and the screen 21A is arched to accommodate the excursion of the push rod 92A.

In this embodiment the push rod 92A is initially of uniform diameter throughout and machined to provide spaced circumferential grooves 150 receiving segmented C-spring 152 washers supporting a V-ring seal 94A between them cooperating with the cylindrical port 82 as supported concentrically by a third C-spider spring 154 received in a third circumferential groove I56 and provided with diverging radiating fingers 83 terminally notched to engage the downstream edge of the wall of the cylindrical port with flow openings between them. In doing this each finger 83 preferably is quarter turned to present itself edgewise to the flow of water through the valve port 82 and the notch can be made in the stamping of the fingers. Preferably the shaft can be relieved without loss of necessary beam strength where it passed through the port 82 for assured full flow of water therethrough.

For manual actuation of the valves a longitudinal channel 104 is formed in the wall of the housing 10, has a narrow opening 101 (FIG. 6) with converginglytapered walls 107, to laterally receive a push rod 106 that is pressed in a radial direction and snapped into longitudinal sliding supported relation with its L-shaped end 108 reciprocably received in a recess 110 molded for that purpose ahead of the wall 98. The front end of the push rod is reversely formed to provide a thumb handle 112 which transmits actuating pressure in a direction holding the rod 106 in the channel 104. The inner end 114 of the L-shaped portion 108 engages the end of the valve stem 96 or push rod 92A. The full flow passage 116 from the valves is U-shaped as indicated in FIG. 5 around the recess 110 to the forward part of the compartment which removably receives dual mix jet pumps operating in tandem.

The arrangement of the jet pumps 111 and 113 is within a unitizing shell 115 for ready change for differ ent chemicals and proportions; The exterior closely follows the substantially cylindrical compartment H8 area in the housing as sealed at opposite ends with respect thereto by O-rings 117 to provide a minimized space or reservoir 107 for a chemical concentrate. The inlet to the jet pumps for the water is at 109 and the concentrate is aspirated to the concentrate compartment 118 through the depending nipple 103 from a concentrate bottle 130 by a disconnectable flexible hose 138 and dip tube 140 that minimize the height of the lift for the concentrate.

Each pump includes a tapering converging throat 136 spaced a short distance from a mixing chamber 137 to provide a gap 105 that leads through diverging walls 139 to the outlet end 26 of the housing 10.

The second stage jet pump 111 extends the length of the housing compartment and is off-set radially an appreciable distance from the axis thereof to accommodate other elements. Along the side of the converging throat 136A of jet pump 111 is the primary jet pump 113 with a converging entrance 121 for water, ajet gap 105A for concentrate and a mixing chamber 137A with diverging walls 139A. The gap 105A of the primary jet pump is in communication with the space 118 to aspirate concentrate and the outlet of its mixing chamber is in communication with the throat of the gap 1058 of the secondary jet pump 113. A first dilution proportioning is accomplished in the first jet and the final mixture proportioning is accomplished in the second stage, thereby providing a high degree of constancy and accuracy above 10 p.s.i.g. of water pressure. A ball 135 is disposed at the outlet of the primary jet pump where it normally resides in a cavity 133 during operation but enters the tapered space 123 as guided by cage pins 141 to serve as a back flow check valve if there is any tendency for back flow of mixture through the primary jet pump 113.

Thereby the concentrate is diluted and mixed with one proportion, and that mixture further diluted and mixed for discharge at the outlet of the housing. The action of the jet pumps provide a quite' accurately proportional mixture for dispensing through a fixed but interchangeable, spray nozzle on the front end for opera tion at water pressures which generally are well above approximately p.s.i.g. Below this pressure the spring 44 is set to actuate the valves 46 and 63 as for the antiback-flow purposes already described. The nozzle can be rotated as sealed by an O-ring 63 when held by a flange nut 65 threaded as already mentioned to a nonconventional thread 28.

For the purpose of assisting the constancy of the mixture ratio a depending stud 120 is provided which is cross kerfed at 122 and apertured at 124 to receive the free end of a flexible looped hanger strap 126 secured thereto by a grommet 127. The strap at its free ends has a snap fastener 128 for receiving and supporting a conventional bottle 130 or container of concentrate solution by and close to the handle 132. The hanger 126 releasably. engages the handle 132 of the bottle in supporting relationship and on the nipple 103 leading to the chamber 107, a flexible tube 138 of fixed length is connected between the nipple and a dip tube 140 in the bottle 130.

As shown in HO. 1, the assembly is manipulated by one hand, either right or left, with the fingers around the housing used as a handle and the thumb is disposed in place to operate the flow valve push rod 106.

6 With the flexible hose l7, hanger 126 and tube 138, a

person can manipulate, aim and direct the spray 142 in any direction without moving the bottle other than conveniently to carry it with the operator as the operator moves from place to place.

Ease of cleaning, servicing, storing and the use of the device are apparent from the description set forth in the preferred embodiment and the Summary of the lnvention.

The phrase gauge pressure" employed herein means a pressure above atmospheric pressure sometimes specifically referred to as positive gauge pressure.

From the drawings the description relating thereto and the appended claims, it will be appreciated that a jet pump having two or more stages provides for better accuracy and control of the dilution ratios as well as an extended range of such ratios with respect to variations in water supply pressures; the energy transfer process never creates any negative pressure than is needed to draw the concentrate into the device and the variation of ratio with pressure changes is negligible over a wide range of input pressures; the use of the diverging energy converter provides pressurized output capable of an exceptionally good swirl-nozzle spray pattern; wide open energy transfer chambers along with full flow larger tubing and fittings are not easily clogged by wettable powders nor unduly restrictive to the passage of viscous concentrates; and the very high turbulence created by the energy transfer process within the energy converters assures homogenous blending of the output spray solution.

According, the advantages of the spray device are:

a. Maintenance of a practically constant dilution ratio regardless of variations in input pressure;

b. Wide specification limits are provided for water pressures from l() to I00 p.s.i.g. and water temperatures as high as the material of the parts will permit, with the preferred materials used being polypropylene or the like, anodized aluminum. and synthetic seal materials.

c. Quick change construction of matched jet pump and nozzle enable 1 to 7 gallons per minute dispensing', mixture ratios up to 20:1 with a single stage jet pump and up to 200:1 with two stage jet pumps; any cone spray to to 30 and utilize a mixture of any viscosity concentrate capable of flow ing.

d. A thumb operated hydraulically powered valve for instant and exact control of two different flow rates;

e. Automatic flow cut-off whenever input pressure is insufficient for satisfactory operation;

f. Extra large concentrate tubing and ports;

g. A slim-line gun dispenser that is easy to grip with a balancing hing like suspension of concentrate container below for short lift;

h. Corrosion resistant construction throughout;

i. Larger mouth, one-gallon container with open mouth or vented cap can be used for suspension including original shipping containers with concentrate already in them;

j. Extra large valve ports assure insignificant pressure loss through valves up to 7.5 gal. per min. flow with a housing approximately one inch in diamter.

What is claimed is:

1. In a safety device for potable water supply and distributing system having a manually valved outlet,

a housing defining a flow compartment connected releasably to the outlet having an inlet port, an out- 9 let and a valve port opening to atmosphere disposed intermediate the inlet and outlet;

an inlet valve closing against the inflow of potable water at the inlet;

a vent valve in communication with said opening and opening inwardly to vent the compartment to atmospheric pressure;

means interconnecting and coordinating said valves to open one while closingthe other; and

resilient means under pressure coacting with the interconnecting means to close said inlet valve when the opening force of supply water upon the inlet valve and the closing forces of water pressure in said compartment upon the vent valve drops below a predetermined gauge pressure.

2. The device defined in claim 1 in which said valves are slide valves closing cylindrical ports.

3. The device defined in claim 1 in which the valves and ports have substantially the same areas exposed to the pressure in said compartment.

4. The device defined in claim 1 in which said resilient means closes said inlet valve when the combined atmospheric pressure on the vent valve and the resilient means urging the opening of the vent valve exceeds the positive gauge opening pressure of the water supply upon the inlet valve.

5. The device defined in claim 1 in which said resilient means closes said inlet valve when the closing pressures upon the inlet valve of the resilient means and the pressure in the compartment exceeds the opening pressure upon the inlet valve.

6. The device defined in claim l including ajet mixing pump in said outlet establishing in operation a back pressure in the compartment upon the inlet valve.

7. The device defined in claim 6 in which the inlet pressure and compartment pressure vary proportionately and said resilient pressure is a varying pressure diminishing with closure movement of the inlet valve.

8. The device defined in claim 6 in which the compartment back flow closing pressure upon the inlet valve is dropped to atmospheric pressure by the opening of said vent valve immediately following the initial closure of the inlet valve.

9. The device for use at the dispensing end of a watering hose having a resilient expansible wall under water pressure;

a housing secured to the dispensing end having a compartment passage therethrough to a dispensing end and a lateral opening in communication with the atmosphere;

an inlet valve adjacent said end opening with the flow of water under pressure into said compartment;

a vent valve closing said lateral opening under said pressure in the compartment;

means urging closure of said inlet valve at a predetermined low gauge pressure;

means interconnecting said inlet valve and vent valve to open said vent valve upon closing of said inlet valve; and

aspirating means in said compartment adjacent to the outlet of said compartment actuated by the flow of water through said compartment above said predetermined gauge pressure upon the water.

10. The device defined in claim 9 in which water pressure in said compartment upstream to said aspirat- 10 ing means exerts an opening pressure upon the inlet valve substantially equal to its closing pressure exerted upon said vent valve when closed, said vent valve being directly exposed to the path of flow of water through 5 the compartment.

11. The device defined in claim 9 including'an outlet means at said dispensing end having an unconventional thread thereon for interchange of specific attachments that are-continuously open to atmosphere.

l2. ln a device of the class described the combination of a housing defining a water chamber having a water inlet connectable to a pressurized potable water supply and an outlet;

a manual valve controlling outflow of water under pressure through said outlet;

a back flow check valve opening said inlet in response to a predetermined rise in pressure differentials between the chamber and water supply pressure when the manual valve is closed; and

means for venting the chamber directly to atmosphere when the pressure in the chamber drops to a predetermined low gauge pressure and the manual valve is open.

13. The device defined in claim 12 in which said means is a safety relief valve venting to atmosphere and connected to said back flow check valve for positive coaction between them to open one while closing the other.

14. The device defined in claim 13 in which the pressure flow area of the venting valve exposed to the chamber may be substantially greater than that of the check valve.

15. The device defined in claim 12 in which said venting means includes a resilient element urging said back flow check valve to its closed position to determine a gauge pressure at which the back flow check valve will open.

16. The device defined in claim 12 in which the valves are slide valves with cylindrically walled ports.

17. A device of the class described comprising an elongated housing having a wall with an inwardly offset wall portion between a water chamber and a mixing chamber including an axial flange defining a vent valve port and a cylindrical main valve port interconnecting the two chambers;

a flanged sleeve means at the inlet of the water receiving chamber defining a cylindrical inlet port; reciprocating valve members slidably received in said ports;

means interconnecting the vent port valve member and the inlet port valve member for coaction in which one valve is closed while the other is opening with momemtary overlapping of their closing;

resilient means interengaging the inlet port valve and main port valve urging the closure of both and the opening of the vent port valve.

18. The device defined in claim 17 including a jet pump in the mixing chamber, said water chamber being open continuously to atmosphere through the jet pump when said main port valve is open;

said jet pump including a converging energy converter, and a diverging energy converter with an energy transfer chamber between them;

a nozzle mounted on the outlet end of the housing. 

1. In a safety device for potable water supply and distributing system having a manually valved outlet; a housing defining a flow compartment connected releasably to the outlet having an inlet port, an outlet and a valve port opening to atmosphere disposed intermediate the inlet and outlet; an inlet valve closing against the inflow of potable water at the inlet; a vent valve in communication with said opening and opening inwardly to vent the compartment to atmospheric pressure; means interconnecting and coordinating said valves to open one while closing the other; and resilient means under pressure coacting with the interconnecting means to close said inlet valve when the opening force of supply water upon the inlet valve and the closing forces of water pressure in said compartment upon the vent valve drops below a predetermined gauge pressure.
 2. The device defined in claim 1 in which said valves are slide valves closing cylindrical ports.
 3. The device defined in claim 1 in which the valves and ports have substantially the same areas exposed to the pressure in said compartment.
 4. The device defined in claim 1 in which said resilient means closes said inlet valve when the combined atmospheric pressure on the vent valve and the resilient means urging the opening of the vent valve exceeds the positive gauge opening pressure of the water supply upon the inlet valve.
 5. The device defined in claim 1 in which said resilient means closes said inlet valve when the closing pressures upon the inlet valve of the resilient means and the pressure in the compartment exceeds the opening pressure upon the inlet valve.
 6. The device defined in claim 1 including a jet mixing pump in said outlet establishing in operation a back pressure in the compartment upon the inlet valve.
 7. The device defined in claim 6 in which the inlet pressure and compartment pressure vary proportionately and said resilient pressure is a varying pressure diminishing with closure movement of the inlet valve.
 8. The device defined in claim 6 in which the compartment back flow closing pressure upon the inlet valve is dropped to atmospheric pressure by the opening of said vent valve immediately following the initial closure of the inlet valve.
 9. The device for use at the dispensing end of a watering hose having a resilient expansible wall under water pressure; a housing secured to the dispensing end having a compartment passage therethrough to a dispensing end and a lateral opening in communication with the atmosphere; an inlet valve adjacent said end opening with the flow of water under pressure into said compartment; a vent valve closing said lateral opening under said pressure in the compartment; means urging closure of said inlet valve at a predetermined low gauge pressure; means interconnecting said inlet valve and vent valve to open said vent valve upon closing of said inlet valve; and aspirating means in said compartment adjacent to the outlet of said compartment actuated by the flow of water through said compartment above said predetermined gauge pressure upon the water.
 10. The device defined in claim 9 in which water pressure in said compartment upstream to said aspirating means exerts an opening pressure upon the inlet valve substantially equal to its closing pressure exerted upon said vent valve wheN closed, said vent valve being directly exposed to the path of flow of water through the compartment.
 11. The device defined in claim 9 including an outlet means at said dispensing end having an unconventional thread thereon for interchange of specific attachments that are continuously open to atmosphere.
 12. In a device of the class described the combination of a housing defining a water chamber having a water inlet connectable to a pressurized potable water supply and an outlet; a manual valve controlling outflow of water under pressure through said outlet; a back flow check valve opening said inlet in response to a predetermined rise in pressure differentials between the chamber and water supply pressure when the manual valve is closed; and means for venting the chamber directly to atmosphere when the pressure in the chamber drops to a predetermined low gauge pressure and the manual valve is open.
 13. The device defined in claim 12 in which said means is a safety relief valve venting to atmosphere and connected to said back flow check valve for positive coaction between them to open one while closing the other.
 14. The device defined in claim 13 in which the pressure flow area of the venting valve exposed to the chamber may be substantially greater than that of the check valve.
 15. The device defined in claim 12 in which said venting means includes a resilient element urging said back flow check valve to its closed position to determine a gauge pressure at which the back flow check valve will open.
 16. The device defined in claim 12 in which the valves are slide valves with cylindrically walled ports.
 17. A device of the class described comprising an elongated housing having a wall with an inwardly offset wall portion between a water chamber and a mixing chamber including an axial flange defining a vent valve port and a cylindrical main valve port interconnecting the two chambers; a flanged sleeve means at the inlet of the water receiving chamber defining a cylindrical inlet port; reciprocating valve members slidably received in said ports; means interconnecting the vent port valve member and the inlet port valve member for coaction in which one valve is closed while the other is opening with momemtary overlapping of their closing; resilient means interengaging the inlet port valve and main port valve urging the closure of both and the opening of the vent port valve.
 18. The device defined in claim 17 including a jet pump in the mixing chamber, said water chamber being open continuously to atmosphere through the jet pump when said main port valve is open; said jet pump including a converging energy converter, and a diverging energy converter with an energy transfer chamber between them; a nozzle mounted on the outlet end of the housing. 